Getting undefined method `klass' for nil:nilclass - Railscast #197 - ruby-on-rails-3.1

Hi all I followed Ryan Bates' railscasts on nested models and form, but I am getting getting undefined method `klass' for nil:nilclass. I am pretty sure it is due to the the link_to_add_fields since everything was working prior. Below is my error and other relevant code and I'm using Rails 3.1. I did a lot of googling and did not find any to solve my problem, so if you guys could help me out I would really appreciated it. Thanks for your help.
_form.html.erb
<%= form_for(#organization) do |f| %>
<% if #organization.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(#organization.errors.count, "error") %> prohibited this organization from being saved:</h2>
<ul>
<% #organization.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
<% end %>
</ul>
</div>
<% end %>
<div class="field">
<%= f.label :name %><br />
<%= f.text_field :name %>
</div>
<div id="restaurant_field" class="field">
<%= f.fields_for :restaurants do |builder| %>
<%= render 'organizations/partials/restaurant_fields', :f => builder %>
<% end %>
</div>
<div class="actions"><%= f.submit %></div>
<% end %>
_restaurant_fields.html.erb
<p class="fields">
<%= f.label :name, "Restaurant Name" %><br />
<%= f.text_field :name %>
<%= link_to_remove_fields "Remove", f %>
application_helper.rb
module ApplicationHelper
def link_to_remove_fields(name, f)
f.hidden_field(:_destroy) + link_to_function(name, "remove_fields(this)")
end
def link_to_add_fields(name, f, association)
new_object = f.object.class.reflect_on_association(association).klass.new
fields = f.fields_for(association, new_object, :child_index => "new_#{association}") do |builder|
render(association.to_s.singularize + "_fields", :f => builder)
end
link_to_function(name, h("add_fields(this, \"#{association}\", \"#{escape_javascript(fields)}\")"))
end
end
application.js
function remove_fields(link) {
$(link).prev("input[type=hidden]").val("1");
$(link).closest(".fields").hide();
}
function add_fields(link, association, content) {
var new_id = new Date().getTime();
var regexp = new RegExp("new_" + association, "g");
$(link).parent().before(content.replace(regexp, new_id));
}

I found that the link_to_add_fields helper won't work if the associated model is describe by a has_one. The has_one means the association does not get the klass object.
You can determine this is your problem by changing your relationship to has_many :object + s (your object name with an s) and passing your object in plural to link_to_add_fields.

You have done the same thing as this person here
Edit: (error on my part)
I am assuming you have an link_to_add_fields below this line
<%= link_to_remove_fields "Remove", f %>
as it seems that the _restaurant_fields.html.erb partial is incomplete. (no closing tag)
</p>
Remove the link_to_add_fields outside of the f.fields_for
That should solve the klass error.

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Showing c:/Sites/blog/app/views/articles/new.html.erb where line #8 raised:
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How to solve ParameterMissing error using ROR

Please help me to solve the below error.
Error:
ActionController::ParameterMissing in CustmersController#create
param is missing or the value is empty: users
When i am submitting the data,this error is coming.
My code is as follows
views/custmers/new.html.erb
<h1>Enter your data here</h1>
<center>
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<p>
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class CustmersController < ApplicationController
def index
end
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#users=Custmer.new
end
def show
end
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#users=Custmer.new(user_params)
if #users.save
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private
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class Custmer < ActiveRecord::Base
EMAIL_REGEX = /\A[A-Z0-9._%+-]+#[A-Z0-9.-]+\.[A-Z]{2,4}\z/i
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validates :email, :presence => true, :uniqueness => true, :format => EMAIL_REGEX
validates :phoneno, presence: true,length: {minimum: 10}
end
I am using rails version-4.2.0 and ruby version-1.9.3.Please help me to resolve this error.
If you look at the stack trace accompanying your error, you could tell definitely where the problem is -- look for the first line in the stack trace that refers to your code (and not library code).
But a fair guess is the require(:users) line in your controller. It looks like you either copy/pasted this code from another controller, or changed the name of your controller after generating it as part of your scaffold.
It should be requires(:custmer) instead, as that is the class of the thing you're submitting.
As a general approach, you should follow the standard Rails practices for naming things, throughout. If you really want to use the misspelled, Custmer class, have at it, but use #custmr inside your controller and views to refer to an instance, not #users.

Rails 4 Error: undefined method[]' for nil:NilClass`

I'm trying to setup a messaging system in my site using the Mailboxer gem in Rails 4.
When my app gets to this code:
def fetch_params(key, *subkeys)
params[key].instance_eval do
case subkeys.size
when 0 then self
when 1 then self[subkeys.first]
else subkeys.map{|k| self[k] }
end
end
it returns the error: undefined method '[]' for nil:NilClass
I've tried to figure this out, but I'm not very experienced. I've been following this tutorial: http://jamestansley.com/2014/02/22/customizing-the-mailboxer-ruby-gem-2/
I tried removing the line of code returning the error just to see what would happen, after which I received the error wrong number of arguments (1 for 2..6).
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view/conversations/_form:
<%= simple_form_for :conversation, url: :conversations do |f| %>
<%= f.input :recipients %>
<%= f.input :subject %>
<%= f.input :body %>
<div class="form-actions">
<%= f.button :submit, class: 'btn-primary' %>
<%= submit_tag 'Cancel', type: :reset, class: 'btn btn-danger' %>
</div>
<% end %>
view/conversations/show:
<h1><%= #conversation.subject %> </h1>
<!--may have to work on this view. don't know if i did the haml conversion correctly-->
<h1> <%= conversation.subject %> </h1>
<ul>
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<%= message = receipt.message %>
<h3><%= message.subject %> </h3>
<p><%= message.body %> </p>
</ul>
<% render 'messages/form', conversation: conversation %>
<% end %>
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add form (non-nested) dynamically in rails

pls can someone explain how I can dynamically add another copy of a form in rails?...been working on this for almost 2hrs. I messed around with .clone() and .appendTo in jquery, but it didnt work. Also, most of the materials I found online (like on railscast #196 and stackoverflow) focused heavily on nested forms. My form is nested, but I actually just want to add the parent form again. The photos which are nested use the html multiple attributes so I'm guessing that will handle multiple files upload for each parent form (btw I'm using paperclip).
If I just need to modify the railscast code please let me know.
Thanks.
<%= form_for(#user_book, html: { multipart: true }) do |f| %>
<% if #user_book.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(#user_book.errors.count, "error") %> prohibited this user_book from been saved:</h2>
<ul>
<% #user_book.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
<p>hello</p>
<% end %>
</ul>
</div>
<% end %>
<%= f.text_field :title, placeholder: "enter title...", id: "book_title" %>
<%= f.text_field :category, placeholder: "enter category..." %>
<%= file_field_tag 'user_book[user_book_photos_attributes][][photo]', :multiple => true do |p| %>
<%= p.file_field :photo %>
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<div class="actions">
<%= f.submit %>
</div>
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I'm very new to Rails 3 and I've followed some tutorials and now I'm trying to "play" with the code created. I have followed the tutorial from http://guides.rubyonrails.org/getting_started.html
I'm am trying to render the form for new posts on the homepage with this code:
<%= render :partial => "posts/form" %>
The posts/_form.html.erb looks like this:
<%= form_for(#post) do |f| %>
<% if #post.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(#post.errors.count, "error") %> prohibited this post from being saved:</h2>
<ul>
<% #post.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
<% end %>
</ul>
</div>
<% end %>
<div class="field">
<%= f.label :name %><br />
<%= f.text_field :name %>
</div>
<div class="field">
<%= f.label :title %><br />
<%= f.text_field :title %>
</div>
<div class="field">
<%= f.label :content %><br />
<%= f.text_area :content %>
</div>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
and this is the error I get:
undefined method `model_name' for NilClass:Class
Extracted source (around line #1):
1: <%= form_for(#post) do |f| %>
2: <% if #post.errors.any? %>
3: <div id="error_explanation">
4: <h2><%= pluralize(#post.errors.count, "error") %> prohibited this post from being saved:</h2>
Trace of template inclusion: app/views/home/index.html.erb
Rails.root: d:/server/cazare
Application Trace | Framework Trace | Full Trace
app/views/posts/_form.html.erb:1:in `_app_views_posts__form_html_erb___794893824_70478136_519766'
app/views/home/index.html.erb:5:in `_app_views_home_index_html_erb__967672939_70487520_0'
I understand that this may seem a piece of cake for some of you but I'm trying to understand how everything works on Rails so I hope you can understand me.
Thanks in advance !
#post variable is not instantiated in the Controller :)
so "#post = Post.new" inside the controller action should do the trick
Rails is attempting to build a form for the object #post. In order to do that, it needs to know what sort of object #post is; that way, it can find any existing data in the object and fill it into the form for you. Rails has a method grafted on to objects called model_name to do the lookup, but it won't be grafted onto NilClass (the class of the nil object).
I suspect that you haven't defined #post anywhere - it's an instance variable of the Controller, so you'd expect the controller to either find #post from the database, or to call #post = Post.new - so it's nil.
In the posts/_form.html.erb,
change
<%= form_for(#post) do |f| %>
to
<%= form_for(Post.new) do |f| %>

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